Honestly, from the way people talk about Mario around here, you'd think it to be the most tired and stale game series ever, that it's completely devoid of innovation.
There it is, that word. "Innovation." The way people throw the word around, they act like it's something that every game requires, that a game can't possibly be enjoyable without somehow doing something new. They say that Mario games are all "rehashes" of the same formula and therefore bad.
Honestly, I don't see what the big deal is. I've bought every single New. Super Mario Bros. game, and I can honestly say that I've enjoyed every one of them a great deal, because the fact remains that they are fun.
Hell, sometimes I actually admire Mario for staying the same. Over the past decade or so, the game industry has been transformed into a bloated mess, with much of it virtually unrecognizable from what it once was. But while other series become become more complex and often overly complicated, Mario games remain the simple fun that they always were.